A major concern for immobile patients and like persons are medical conditions that form clots in the blood, such as, deep vein thrombosis (DVT) and peripheral edema. Such patients and persons often include those undergoing surgery, anesthesia, extended periods of bed rest, etc. These blood clotting conditions generally occur in the deep veins of the lower extremities and/or pelvis. These veins, such as the iliac, femoral, popiteal and tibial, return deoxygenated blood to the heart. When blood circulation in these veins is retarded due to illness, injury, or inactivity, for example, there is a tendency for blood to accumulate or pool. A static pool of blood may lead to the formation of a blood clot. A major risk associated with this condition is interference with cardiovascular circulation. Most seriously, a fragment of the blood clot can break loose and migrate. A pulmonary embolus can form from the fragment potentially blocking a main pulmonary artery, which may be life threatening.
Vascular compression systems find frequent use for improving blood flow in a targeted area of a patient's body (e.g., a limb, such as a leg, foot, or arm). A conventional compression system typically incorporates a compression garment for applying compressive forces to the targeted area. The system delivers intermittent or cyclic pulses of compressed air to at least one inflatable chamber in the garment, which in turn inflates and compresses the body part on which the garment is worn. The cyclic inflation of the compression garment provides a non-invasive method of prophylaxis to reduce the likelihood of incidence of DVT and to improve blood flow.
A major source of inefficiency in any compression system is the waste of energy required to inflate loosely fitted compression garments. Relatively large air volumes are required for establishing the fit during the initial fill and during each subsequent inflation to account for any gaps between the garment and the patient. A user, such as a nurse or the patient, adjusts straps, buckles, wraps, or the like on the garment in an attempt to achieve a comfortable yet effective fit. A crude approach used for determining good fit of the garment involves inserting one or more fingers into the space between the garment and the limb. In addition to a lack of precision, drawbacks of this approach include an inability to monitor fit during use and difficulty in adjusting fit to unusual limb profiles such as large muscles or swollen tissue.